PROBLEM OF LEAD POISONING

Lead poisoning is the number one environmental disease among children in developing countries. The full impact of lead poisoning on the health of children and adults is becoming clearer to most countries, and many governments have begun to take action. Significant health and economic benefits have been realized by those countries which have developed lead prevention programs.

Lead occurs naturally in the earth's crust. When ingested, inhaled, or absorbed through skin, lead is highly toxic to humans. Lead's toxicity has been known for thousands of years; Greek physicians made the first clinical description of lead poisoning in the first century B.C.

Lead is not biodegradable. It persists in the soil, in the air, in drinking water, and in homes. It crosses all social, economical and geographical lines. It never disappears, it only accumulates where it is deposited and can poison generations of children and adults unless properly removed.

At high levels, lead poisoning causes coma, convulsions and death. At low levels - levels far below those that present obvious symptoms - lead poisoning in childhood causes reductions in IQ and attention span, reading and learning disabilities, hyperactivity, impaired growth, behavioral problems, and hearing loss. These effects are long-term and may be irreversible.

World-wide, six sources appear to account for most lead exposure:
1. gasoline additives;
2. food can soldering;
3. lead-based paints;
4. ceramic glazes;
5. drinking water systems; and
6. cosmetic and folk remedies.

Other significant exposures result from inadequately controlled industrial emissions from such operations as lead smelters and battery recycling plants, which contaminate environments and people in the surrounding areas. The highest level of environmental contamination is found to be associated with uncontrolled recycling operations and the most highly exposed adults are those who work with lead.

Developed countries like the US, UK and Germany have taken aggressive steps to combat lead poisoning. In developing countries, however, actions have been slower and sporadic. Within the last decade, reports of lead poisoning in humans have poured in particularly from the developing countries faced with environmental and occupational lead exposure.

In India, as in most developing countries, the main source of lead pollution is automobile exhaust. Although India issued in February 1990 its first National Emission Standards for lead and other pollutants, the recommended permissible limits of lead (0.56 g/L) are still very much higher than those of developed countries like the US, UK, and Germany. In the US, the virtual elimination of leaded gasoline resulted in a 77% decrease in the average blood lead level of the population between 1976 and 1991. In the UK, a 50% drop in gasoline lead levels corresponded with a 20% drop in blood lead levels.

The scope and nature of lead poisoning that recent studies have uncovered are alarming. Here are some hard facts:

  • No level of lead in blood is safe or normal. The disturbing fact is that exposure to extremely small amounts can have long-term and measurable effects in children while at the same time causing no distinctive symptoms.
  • Once lead is absorbed into the bloodstream, some of it is filtered out and excreted, but the rest gets distributed to the liver, brain, kidneys and bones.
  • Lead causes anemia in both children and adults by impairing the formation of oxygen-carrying molecules, beginning at exposures of around 40ug/dl. In adults, small but significant increases in blood pressure result from exposures as low as 5 ug/dl, with no evidence of a threshold below which lead does not affect blood pressure.
  • Other adverse effects in adults include kidney disease and impaired fertility.
  • Hypertension caused by lead exposure contributes to thousands of deaths every year, particularly in men between the ages of 35 and 50.
  • Children and pregnant women are particularly susceptible to lead poisoning.
  • Children's digestive system absorbs up to 50% of the lead they ingest. The high retention occurs from birth to age 6 when the brain is developing and lead interferes with its development. By the time physical symptoms are evident - headache, lethargy or hyperactivity, nausea, stomach aches, vomiting, and constipation - significant brain damage has already occurred. Abdominal pain, vomiting and constipation help greatly to differentiate lead from infectious disease that cause similar symptoms and are common, but result in diarrhea.
  • Children pick up lead dust from the floor, from their toys and from pets. They ingest lead when they put their hands in their mouths, when they eat with their hands, when they suck their thumbs, when they ingest soil. Lead compounds used in paint taste sweet, encouraging small children to lick or chew paint chips or chalky paint residue. A single chip of paint of the size of a thumbnail contains 1 gram of lead and a few such chips can raise the intake of lead to 1,000 times the acceptable limit.
  • Blood lead levels in children of around 10 ug/dl are associated with disturbances in early physical and mental growth and in later intellectual functioning and academic achievement. These persist into adulthood and may be irreversible.
  • Progressive elevation of blood lead levels in a child's system can cause a potential genius to drop to an average achievement level and an average child to become learning disabled. Studies have shown as much as a 5.8 decline in IQ (on a scale where 100 is average) for every 10 micrograms increase of lead in blood levels. Long-term consumption of low levels of lead can be more dangerous than a single ingestion of concentrated lead.
  • The fetuses of pregnant women are gravely affected by lead exposure since lead can pass through the placenta directly into the baby. When an expectant mother maintains a poor diet, the problem is compounded since she will start breaking down bone to release calcium and other minerals, thereby releasing lead stored in the bones which passes to the developing baby. High lead exposure probably results in fetal death.
  • Deficiency of iron, calcium and zinc increase absorption and effects of lead.
  • The Centers for Disease Control and Prevention (CDC), USA, has developed various classes of elevated blood lead levels in children. If a child's level is greater than 45 ug/dl, chelation treatment and exposure reduction should start within 48 hours, while levels at or above 70 ug/dl are a medical emergency. Even higher levels cause swelling of the brain or encephalopathy. Children with levels above 120 ug/dl may die unless immediately treated.
  • Childhood lead poisoning is typically more severe in developing countries due to inadequately controlled industrial emissions, unregulated cottage industries, and cultural practices such as folk medicines containing lead.
  • The World Health Organization estimates that 15-18 million children in developing countries are suffering from permanent brain damage due to lead poisoning. Hundreds of millions of children and pregnant women in practically all the developing countries are exposed to elevated levels of lead.

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